During certain types of surgery, particularly in connection with chest cavity surgery, the patient frequently loses large amounts of blood. Ordinarily, the lost blood is aspirated away and the patient is given a transfusion of donated blood to make up for the lost blood. An alternative arrangement is to provide an auto transfusion device which will collect the blood lost by the patient and transfuse this blood into the patient's circulatory system. Such an apparatus is disclosed in our copending application referred to hereinbefore.
There are disclosed in the prior art various systems for auto transfusion. For example, in U.S. Pat. No. 3,191,600 (Everett) an auto transfusion apparatus is disclosed which includes a vacuum source and a plurality of suction tips for immersion in pools of blood. The blood is collected in a collection chamber and is returned to the patient through a oneway valve. Another auto transfusion device is disclosed in U.S. Pat. No. 3,492,991 (Dyer) and includes a container equipped with a filter through which the blood is gravity fed back to the patient. In U.S. Pat. No. 3,993,067 (Schachet et al) an auto transfusion device is disclosed in which the blood is forced back into the patient by pressure in the collection chamber. Still another auto transfusion device is disclosed in U.S. Pat. No. 4,047,526 (Reynolds et al). This patent discloses a collection chamber in which blood is continuously aspirated. A blood bag with an outwardly urged spring is connected to the collection chamber to withdraw some of the blood therefrom. The blood collected in the blood bag is then later reintroduced into the patient. There has also been disclosed in the prior art a spring operated device which forces blood from a blood bag into the patient. Such a device is disclosed in U.S. Pat. No. 3,565,292 (Jinotti).
While auto transfusion has been disclosed in the prior art, there is a need for an air purge unit which will effectively prevent the possibility of air being reintroduced into the patient's circulatory system which could lead to disastrous consequences. According to the present invention, an air purge unit is provided which ensures that all air within the collection chamber for the blood is eliminated before the blood is reintroduced into the patient's circulatory system.